During my first week in Chicago, I cared for as many children with gunshot wounds as I had seen over the course of two years in Boston. Last year alone, we treated 54 children with gunshots at my hospital, more than the deadliest school shooting in America’s history.

But you really shouldn’t be surprised. A couple years ago I looked at changes in age among homicide victims and perpetrators in Chicago. In particular, I wanted to check something—sometimes people who lived in Chicago when it was unquestionably more violent, decades ago, lament how much more violent young people are today. And it turned out that young people did in fact make up a much higher percentage of victims and perpetrators recently than in the more distant past:

In 1965, victims from 15-24 years old made up 17 percent of the total [number of homicide victims in Chicago]. In 1975, 29 percent. In 1985, 29 percent. In 1995, 42 percent. In 2005, 40 percent. Last year, it was 44 percent.

The change in offender age is pretty similar. In 1965, offenders from ages 15-24 made up about 30 percent of all homicide-level offenders; in 1995, it was about 65 percent.

It also appears that, today, Chicago homicide victims are significantly, if not dramatically, younger than victims in other big cities. Using data from RedEye’s homicide tracker, I calculated the average age of homicide victims in recent years. In 2012, it was 29.3; in 2013, 27.3; in 2014, 28; in 2015, through early July, it was 28.4.

Compare that to Los Angeles, where the average age has risen from 30 to 34 years from 2000 to 2014. There are theories, but no one really knows why. The most recent data I could find for New York was 2012, when the average age was 32. In Baltimore, “the average age of city homicide victims in 2013 was 31, unchanged from recent years.” As of 2008, the national average age was 32.7.